Teacher strike in Portland, Oregon

Students from Lincoln high school demonstrate in support of teachers in contract negotiations during a school walkout in Portland

Students from Lincoln high school demonstrate in support of teachers in contract negotiations during a school walkout in Portland, Oregon February 5, 2014. REUTERS/Steve Dipaola (UNITED STATES - Tags: EDUCATION CIVIL UNREST POLITICS)

Portland's 2,828 teachers have been engaged for months in contentious off-and-on negotiations with the district on a new three-year contract, and the strike authorization vote clears the way for a strike on February 20 if no settlement is reached, the Portland Association of Teachers said late Wednesday. (Reuters)